1. Field of the Invention
This invention relates to a pipe stopper, stopper kit and method, and more particularly to a pipe stopper, stopper kit and method adapted to effect a seal within a fluid-carrying pipe.
2. Description of Related Art
In the maintenance or renewal of domestic low pressure gas supply systems it is frequently necessary to cut off the gas supply temporarily at a distance remote from the access point, to allow such maintenance or renewal to be carried out. Typically such a requirement arises, for example, when exchanging or repairing a meter control cock, or an elbow, under "live" conditions, or when stopping off a gas supply at a point outside the consumer's premises. In some circumstances it is also necessary to cut off the gas supply from a premises for an extended period, for example, if the gas supply is to be withdrawn from a consumer for some reason.
It has previously been proposed to insert into the pipe a hollow tube having at one end an inflatable sack which is pushed down the pipe in a deflated condition and then inflated to block the pipe. However, with such a device it is still necessary for the inflation tube to remain in position, and this is often an inconvenience when carrying out repair work. There is therefore a continuing requirement for a system which will enable a pipe to be blocked at a distance remote from the access point without leaving any part or fitting in the pipe protruding from or interfering with the access point.
In addition to the above requirement, the point at which it is required to block the pipe is often beyond one or more pipe bends or elbows, and therefore desirably any blocking system should be able to negotiate at least one, and preferably two or more such bends or elbows.
In certain circumstances an improvement in the sealing capability of the known blocking system would also be desirable. For example, a public utility now requires that a seal for a domestic gas pipe should be able to withstand a pressure of up to 100 millibars for a minimum of 5 minutes with a maximum pressure loss of 1% over that time, and this is difficult to achieve with existing blocking methods.